I'm also in too deep to ever get my money back at this point!
I have over $15,000 into my gmt400, and would struggle to sell it for $5,000. Maybe they will gain value as they age? I am hoping...
Most of the money that I put into my gmt400 was to try and make it as good/better than my 2015 f150 with the 2.7 Ecoboost/6 speed trans. I made the gmt400 as good at towing our camper, but it still isn't as good at daily driving.
So... I have $15k into a gmt400 that is worth 5K, and an f150 that does the same job, and you could buy for maybe 20k. The kicker is that you could sell the f150 for 20k also...
The gmt400 is cheaper/easier to fix if something goes wrong, but the newer stuff isn't terrible.